It is often necessary to determine the quantity of liquid stored in a tank or the quantity of granular material, such as grain, stored in a bin. Conventionally this is accomplished by climbing to the top of the container and looking in. Remote sensors are used as well which employ various techniques including photo-electric and ultra-sonic techniques which are costly. Changes in resistance of an element as the container level changes has been measured and correlated to bin level, however foreign material and corrosion can cause changes in resistance of the contact points and so is not dependable. Liquid tanks can also use sight glasses mounted on the tank exterior.
A dependable and economic level sensor which can be mounted on the interior of a liquid or particulate container would be beneficial.